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Biomedical subjects

D G Mills

Publications and source records attributed to D G Mills.

13 recordsLinked to original sources
PubMed1994

Inversion in the steady state: contrast optimization and reduced imaging time with fast three-dimensional inversion-recovery-prepared GRE pulse sequences.

PURPOSE: To evaluate the differences in contrast between 1-second delay and zero delay (for magnetization recovery) before the preparation radio-frequency pulse in three-dimensional, inversion-recovery (IR) fast gradient-echo (GRE) acquisitions. MATERIALS AND METHODS: Mathematical simulations and measurements of brain image contrast were performed with healthy volunteers and 10 patients. RESULTS: The zero-delay sequence generated T1-weighted contrast similar to that obtained with 1-second delay but was accompanied by a substantial reduction in imaging time. However, the zero delay prohibits full recovery of the longitudinal magnetization. Hence, the signal null characteristic of IR experiments is not easily observed, since it occurs (as a function of tissue T1) at very short inversion times (< 150 msec). CONCLUSION: T1-weighted contrast comparable with that of magnetization-prepared rapid GRE sequences with a 1-second delay and preparation time (TP) of 600-700 msec can be achieved in less time by using a zero delay and a shorter TP (400-500 msec).

Brain↗
PubMed1990

Three-dimensional gradient-recalled MR imaging as a screening tool for the diagnosis of cervical radiculopathy.

The purpose of the study was to implement and assess a fast-screening, three-dimensional Fourier transformation (3DFT) MR sequence for the cervical spine. This sequence maintains adequate signal-to-noise and image contrast similar to gradient-recalled echo two-dimensional Fourier transformation (2DFT) imaging. Thirty patients with radiculopathy were examined with 3DFT gradient-recalled echo imaging. The data set consisted of 60 contiguous 1.5- to 2.0-mm-thick axial slices with a total coverage of 9 to 12 cm. In 10 patients, comparison was made with 4-mm-thick axial T1-weighted spin-echo 2DFT or gradient-recalled echo 2DFT studies. With the use of a volume acquisition, adequate signal-to-noise and image contrast similar to T2-weighted gradient-recalled echo 2DFT acquisitions were obtainable. Coverage was improved despite the use of thinner sections without interslice gap. Thin-section 3DFT provided superior detail of acquired foraminal and spinal canal stenosis and disk morphology. Limitations included increased sensitivity to patient motion and "wraparound" artifact in the slice-select direction. Overall, diagnostic confidence was improved with 3DFT owing to the reduction of partial volume artifact. We have adopted this technique as the primary screening method for diagnosing cervical radiculopathy.

Cervical Vertebrae↗
PubMed1984

Occupational exposure to cyclophosphamide.

Several lines of research have demonstrated the risk of occupational exposure of health-care personnel to anticancer drugs. Urine samples from two nurses working in a cancer clinic were analysed for cyclophosphamide (CP) by gas chromatography after they had prepared the drug for treatment. Since the drug might be absorbed through the skin, urine samples from five volunteers were also examined after a solution of CP had been applied topically to the cubital fossa area. Variable quantities of intact CP were identified in samples from the volunteers collected over 24 h, but in most cases the drug was evident only in urine samples given more than 6 h after application. CP was found in several urine samples from the nurses, but the quantities of CP in these samples were not related to the amounts of drug handled. The identity of CP was confirmed by gas-chromatography/mass-spectrometry. CP appeared sooner in the urine samples from the nurses than in those from the volunteers, suggesting a faster route of absorption, perhaps through inhalation of aerosols generated during dissolution of the drug. These findings suggest that the increased levels of mutagenicity observed in urine samples of nurses who worked on oncology wards might have arisen, in part, from metabolites of CP.

Adult↗
PubMed1979

Changes in platelet function and gastrointestinal bleeding following repeated administration of acetylsalicylic acid in the rat and the dog.

Two dogs were prepared with Pavlov pouches of the fundic area of the stomach using standard techniques. During treatment periods of 14 days, 200 mg acetylsalicylic acid (ASA) was introduced into the pouch twice daily by insufflation. One hour after each drug administration the pouch was washed with saline and the fluid assayed for blood. Bleeding from the pouch increased to a maximum on the 3rd or 4th day of the treatment period and subsequently declined such that by the 8th day blood loss was minimal and approximated that found during control periods. Platelet aggregation (in vitro) responses to adenosine diphosphate were significantly (p less than 0.01) inhibited on day 3 when aggregation curve heights were reduced by 66.2 +/- 13.11% (mean +/- SEM) from control values. On day 7 and during the ensuing 7-day period when ASA was given twice daily, the heights of aggregation responses were reduced by only 20-30% from controls. These responses were significantly (p less than 0.001) greater than those found on day 3. Similar changes in platelet reactivity were found in plasma from rats given ASA twice daily for 7 days. Aggregation responses to collagen were depressed by 95.5 +/- 4.49% on day 1 following two doses of ASA. As the treatment period continued, the aggregation responses increased in magnitude until the 7th day they were similar in height to those from control animals. The mechanism involved in this adaptation to ASA treatment seen with these platelets is not known.

Adenosine Diphosphate↗
PubMed1978

Effects of methaqualone on blood platelet function.

To study the mechanism whereby toxic doses of methaqualone cause a bleeding tendency in humans, the effects of methaqualone, diphenhydramine, and the combination of methaqualone plus diphenhydramine on blood platelet function were investigated. Exposure of human platelets in platelet-rich plasma in vitro to final concentrations of methaqualone ranging from 1.1 to 4.5 X 10(-4)) M resulted in nearly complete inhibition of the secondary phase and significant inhibition of the primary phase of adenosine diphosphate (ADP)--induced aggregation. Both the slope and height of collagen-induced aggregation responses were reduced significantly in vitro by the drug. When methaqualone final concentrations of 1.1, 2.3, and 4.5 X 10(-4) M were studied in the presence of diphenhydramine (1.1, 2.3, and 4.5 X 10(-5) M, respectively), the degree of inhibition of ADP-induced aggregation was only slightly greater (not significant) than that observed with methaqualone. The platelets of rabbits injected intravenously with methaqualone, 10 mg/kg, demonstrated a significantly decreased ability to aggregate with ADP and collagen 30 and 60 min after administration of the drug. These results suggest that a drug-induced defect of blood platelet function may play a role in the bleeding associated with methaqualone toxicity.

Adenosine Diphosphate↗
PubMed1976

Evaluation of Mannich bases and related compounds as inhibitors of mitochondrial function in yeast and inhibition of blood platelet aggregation, blood clotting, and in vitro metabolism of 5-dimethylamino-1-phenyl-1-penten-3-one hydrochloride.

Dimethylamino-1-phenyl-1-penten-3-one hydrochloride (Ia) and 32 analogs were tested for inhibition of respiratory-dependent growth in Saccharomyces cerevisiae. Thirteen of the 33 compounds tested appeared to affect mitochondrial function, since the inhibition of respiratory-dependent growth was statistically greater than the inhibition of growth on fermentable energy sources. Inhibition of mitochondrial function in yeast and growth inhibition of an in vitro culture of human epidermoid carcinoma (KB) were positively correlated since 83% of the compounds tested either had mitochondrial-inhibiting properties and significant activity in the KB test or were inactive in both tests. Similarly, 78% of compounds tested showed murine toxicity and mitochondrial inhibition or had no effect on murine toxicity and yeast mitochondrial function. Injection of Ia into rats resulted in the appearance of blood in the urine and feces. Compound Ia inhibited adenosine diphosphate and collagen-induced aggregation of rat platelets but had no effect on blood clotting. TLC, following incubation of Ia with a rat liver extract, showed that the structure of Ia was not enzymatically modified and indicated activity per se on platelet aggregation and mitochondrial function.

Adenosine Diphosphate↗
PubMedDate not supplied

Three-dimensional gradient-recalled MR imaging as a screening tool for the diagnosis of cervical radiculopathy.

The purpose of the study was to implement and assess a fast-screening, three-dimensional Fourier transformation (3DFT) MR sequence for the cervical spine. This sequence maintains adequate signal-to-noise and image contrast similar to gradient-recalled echo two-dimensional Fourier transformation (2DFT) imaging. Thirty patients with radiculopathy were examined with 3DFT gradient-recalled echo imaging. The data set consisted of 60 contiguous 1.5- to 2.0-mm-thick axial slices with a total coverage of 9 to 12 cm. In 10 patients, comparison was made with 4-mm-thick axial T1-weighted spin-echo 2DFT or gradient-recalled echo 2DFT studies. With the use of a volume acquisition, adequate signal-to-noise and image contrast similar to T2*-weighted gradient-recalled echo 2DFT acquisitions were obtainable. Coverage was improved despite the use of thinner sections without interslice gap. Thin-section 3DFT provided superior detail of acquired foraminal and spinal canal stenosis and disk morphology. Limitations included increased sensitivity to patient motion and "wraparound" artifact in the slice-select direction. Overall, diagnostic confidence was improved with 3DFT owing to the reduction of partial volume artifact. We have adopted this technique as the primary screening method for diagnosing cervical radiculopathy.

Evaluation Studies as Topic↗